Study On The Construction And Optimization Of Ecological Network In The Northeastern Margin Of Ulanbuhe Desert

Based on complex network theory,landscape ecology and GIS spatial analysis technology,the basic ecological situation of the study area was analyzed firstly,and then the potential ecological network of the study area was constructed by using cumulative consumption resistance model,taking into account a variety of factors.Based on a variety of evaluation indicators of complex networks,the topological structure of ecological network in the study area was analyzed.The results showed that the network had strong non-uniformity and poor connectivity,which needed further optimization.Then,based on the edge-increasing strategy of complex network and the synergy of the structure and function of ecological nodes,the potential ecological network of the study area was optimized,and the topology structure and robustness of the optimized network were analyzed.Finally,based on the optimized potential ecological network,using methods including community mining,minimum spanning tree,and Tyson polygon,based on the synergy analysis of the structure and function of ecological nodes,the ecological security pattern of the study area was constructed.The detailed results are as follows:(1)In view of the characteristics of drought,water shortage and fragile ecology in the study area,two factors include vegetation coverage and groundwater depth,which have important influence on the extraction of ecological network,were studied to reflect the basic ecological situation.It was found that vegetation coverage is on the rise,vegetation on the edge of desert expands to the southwest,and desert tends to retreat.Through the principal component analysis of the influencing factors of groundwater depth in the study area,the first five principal components were selected.Using these five principal components,synergistic Kriging interpolation was carried out based on the data of groundwater depth survey points.The results showed that the groundwater depth in the study area increases from southeast to northwest.The basic ecological situation of the study area has improved,but there is still a big gap between the southwest and northeast,and there is still room for improvement.(2)417 ecological sources were extracted by indices including patch area,average NDVI/MNDWI and patch shape index.Using the cumulative consumption resistance model,the ecological cumulative resistance surface of the study area was constructed,the potential ecological corridors and ecological nodes were extracted,and the potential ecological network of the study area was formed.According to the connection relationship between ecological nodes,the potential ecological network was abstracted as the adjacency matrix of complex network.According to the importance of ecological nodes and the cumulative resistance value of potential ecological corridor,the weight of each edge was set by gravity model,and finally the complex ecological network of the study area was formed.(3)The topological structure of the potential ecological network in the study area was analyzed by using a variety of indicators in the complex network theory.The analysis of its basic static characteristics showed that the potential ecological network degree distribution in the study area basically conforms to the power law distribution,and is a scale-free network.The maximum and minimum point weights of the network are 15.37 and 0,and the node weights of most ecological nodes are very small.The network does not have the characteristics of small world.The analysis of its related characteristics shows that the network is weight-degree-dependent and highly non-uniform;the network presents weak heterogeneity and low robustness;the network does not have clustering-degree correlation and is not a hierarchical network.The PageRank value and node betweenness were used to identify the important nodes in the potential ecological network,which are mainly located in the middle of the research area.The core of the network is 3,which is an incomplete network with 546 connectivity.The connectivity of the network is poor and needs further optimization.(4)Based on the structural and functional synergy of potential ecological network in the study area,an edge-increasing optimization strategy for the ecological network in the study area was constructed by combining the edge-increasing strategy according to degrees of nodes.The structural and functional synergy,robustness and topological structure characteristics of the optimized network were analyzed.The results showed that the optimized network has lower non-uniformity,stronger connectivity and stronger robustness.Based on the optimized potential ecological network and the complex network analysis method,the ecological node zoning,key ecological node extraction,skeleton corridor extraction and ecological blind area identification were carried out,and the ecological security pattern of the study area was finally formed.The results showed that there are 17 key ecological nodes in the study area,1288.41 km2 of which 771.83 km2 is the Level 1 blind area,516.58 km2 is the Level 2 blind area.There is 1176.82 km skeleton corridor in the study area.Landscape key components account for a high proportion in zones 9,10.4,7 and 3.These zones are of great importance in regional ecological security,which is the key area to the construction of ecological security.